Drain traps such as described above are installed, for example, in drainage paths which discharge effluent such as drain water of air conditioners to drainage basins. While allowing the effluent received by the receiving unit to flow to the discharge unit through the communicating path, such a drain trap prevents backflow of contaminated air and bad odors by closing the discharge unit using the normally-closed check valve as well as a water sealing action of the effluent stored in the storage unit.
Conventional drain traps include one in which a discharge unit is installed vertically right under a spherical normally-closed check valve in such a way as to penetrate a bottom part of a main body and a storage unit is installed in such a way as to communicate with a part around the normally-closed check valve, excluding a part right under the normally-closed check valve. In this case, the normally-closed check valve is installed in such a way as to close the discharge unit (see, for example, Patent Document 1).
There is another conventional drain trap in which a storage unit is installed in such a way as to communicate with a part right under a spherical normally-closed check valve and a discharge-side storage unit for use to store effluent is provided at a midpoint of a discharge-side communicating path located between the normally-closed check valve and a discharge unit. When effluent in the discharge-side storage unit reaches or exceeds a set amount, the effluent is made to flow to the discharge unit (see, for example, Patent Document 2).
[Patent Document 1]: Japanese Patent Application “kokai” No. 7-71784
[Patent Document 2]: Japanese Utility Model Publication No. 55-51902